Hi All, 

I am facing issue to write test class for this code please help me i am stuck from one month please help me.

public class CommenttoEmail {
   
    public String Commentbody {get;set;}
   
    public String Set_to{get;set;}
    Public String Set_bcc{get;set;}
    public String Set_cc{get;set;}
    public List<String> SetTo {get;set;}
    public List<String> SetCC {get;set;}
    public List<String>  SetBCC{get;set;}
    Public String CaseId {get;set;}
   
    public  String Selec {get;set;}
    public List<String> liststatus {get;set;}
    public boolean flag {set;get;}
    public string Str2;
    
    public String test;
    Public List<string> listall {get;set;} 
     public Attachment attachment {
  get {
      if (attachment == null)
        attachment = new Attachment();
      return attachment;
    }
  set;
  }
    public CommenttoEmail(apexpages.StandardController std)
    { 
        
                
        
        
        liststatus=new List<string>{'New','Escalated','On Hold','Action-Automated Escalation','Agent Research','Scheduled','Awaiting Customer Reply',
            'Awaiting External Response','Awaiting Part','Re-Opened','Closed Successful','Closed Unsuccessful'};
       
        flag=false;
       CaseId=ApexPages.CurrentPage().getParameters().get('Id');
        listall=new List<String>();
        SetTo=new List<String>{};
        SetCC=new  List<String>{};
        SetBCC=new  List<String>{}; 
    }

   
public void senttoEmail()
{
    Case cse = [select id ,CaseNumber ,Status,ContactEmail,subject from case where id=:caseId]; 
    
   
  SetTo=Set_To.split(',');
 
} 
    
public void bccEmail()
{
  SetBCC=Set_bcc.split(',');
}
    
public void ccEmail()
{
    SetCC=Set_cc.split(',');
} 
    public void ss()
    {
        senttoEmail();
        bccEmail();
        ccEmail();
    }
public void attachemail()
{
  listall.addAll(SetTo);
  listall.addAll(SetBCC);
  listall.addAll(SetCC);
  
}
    // this method used for creating  case comment
public pagereference  createCaseComment(){
    ss();
    upload();
attachemail();
sendingEmail();
ChangeStatus();

Case cse = [select id ,CaseNumber ,Status, Contact.name,Account.name,subject from case where id=:caseId];   
String ss=string.join(listall, ',');
String Str1='\n\n';
String Str0='[Recipients:' +ss+']';
String Str3=cse.Contact.name+',\n\n';
String  Reg='\n\n\n Sincerely,\n'+cse.Contact.name+'\n'+cse.Account.name;
   
Str2=Str0+Str1+Str3+Commentbody+Reg;

    
CaseComment cc = new CaseComment(ParentId = cse.Id,CommentBody = str2 , IsPublished=true);
insert cc;
  pagereference pg =new pagereference('/'+CaseId);

return pg;  
   
    }
    // this method used for sending email
public PageReference sendingEmail()
{
 upload();    
Case[] cse = [select id ,CaseNumber ,Status, Contact.name,Account.name,subject from case where id=:caseId limit 1];   
String ss=string.join(listall, ',');

String Str3=cse[0].Contact.name+',\n\n';
String  Reg='\n\n\n Sincerely,\n'+cse[0].Contact.name+'\n'+cse[0].Account.name;
   
Str2=Str3+Commentbody+Reg;
 List<Messaging.Emailfileattachment> fileAttachments = new List<Messaging.Emailfileattachment>();
List<Attachment> Attlist=[select Name, Body, BodyLength from Attachment where ParentId = :caseId];
for (Attachment a :Attlist ){

Messaging.Emailfileattachment efa = new Messaging.Emailfileattachment();

efa.setFileName(a.Name);
efa.setBody(a.Body);
fileAttachments.add(efa);
}



    try{
  
Messaging.SingleEmailMessage semail = new Messaging.SingleEmailMessage();
semail.setToAddresses(SetTo); 
semail.setBccAddresses(SetBCC); 
semail.setCcAddresses(SetCC); 
semail.setSubject(cse[0].Subject); 
semail.setPlainTextBody(Str2);
semail.setFileAttachments(fileAttachments);   
   
Messaging.sendEmail(new Messaging.SingleEmailMessage[] {semail}); 
    
    
    }catch(exception e)
    {}
    return null;
} 
   //This method use for redirect to  current ticket. 
public pagereference redirectCasePage()
{

CaseId=ApexPages.CurrentPage().getParameters().get('Id');
pagereference pg =new pagereference('/'+CaseId);

return pg;   
}
   //This Method used for change status 
    public void ChangeStatus()
    {
        
         List<Case> cse = [select id ,CaseNumber ,Status,subject from case where id=:caseId]; 
        for(Case c:cse){
            if(selec=='New')
            {
                c.Status='New';
            }
            
            if(selec=='Escalated')
            {
                c.Status='Escalated';
            }
            if(selec=='On Hold')
            {
                c.Status='On Hold';
            }
            if(selec=='Action-Automated Escalation')
            {
                c.Status='Action-Automated Escalation';
            }
            
            if(selec=='Agent Research')
            {
                c.Status='Agent Research';
            }
            
            if(selec=='Scheduled')
            {
                c.Status='Scheduled';
            }
            if(selec=='Action-Automated Escalation')
            {
                c.Status='Action-Automated Escalation';
            }
            
            if(selec=='Awaiting Customer Reply')
            {
                c.Status='Awaiting Customer Reply';
            }
            if(selec=='Awaiting External Response')
            {
                c.Status='Awaiting External Response';
            }
            if(selec=='Awaiting Part')
            {
                c.Status='Awaiting Part';
                
            }if(selec=='Re-Opened')
            {
                c.Status='Re-Opened';
            }if(selec=='Closed Successful')
            {
                c.Status='Closed Successful';
                
            }if(selec=='Closed Unsuccessful')
            {
                c.Status='Closed Unsuccessful';
            }
            update c;
        }
           }
// This Method create for status display in custom picklist       
public List<SelectOption> getCaseStatus()
    {
         List<SelectOption> optlist=new List<SelectOption>();
         Case[] cse = [select id ,CaseNumber ,Status,subject from case where id=:caseId limit 1];
       optlist.add(new SelectOption(cse[0].Status,cse[0].Status));
        for(String s:liststatus)
        {
           optlist.add(new SelectOption(s,s));
       
        }    
     return optlist;
    }
    
  //This Method Created for  uploading file 
   public PageReference upload() {
  
    attachment.OwnerId = UserInfo.getUserId();
    attachment.ParentId = CaseId;
    attachment.IsPrivate = true;
    attachment.ContentType = 'image/jpeg';
  
    try {
      insert attachment;
    } catch (DMLException e) {
      ApexPages.addMessage(new ApexPages.message(ApexPages.severity.ERROR,'Error uploading attachment'));
      return null;
    } finally {
      attachment = new Attachment(); 
    }
    ApexPages.addMessage(new ApexPages.message(ApexPages.severity.INFO,'Attachment uploaded successfully'));
    return null;
  }
   
}